Apparatus for the electrolysis of solutions of alkaline chlorids



C. N. RHBER.' APPARATUS FOR THE ELECTROLYSIS 0F SOLUTIONS OF ALKALINE CHLO RIDS.

APPLICATION FILED DEC-12, I918.

Patented May 17, 1921.

UNITED STATES ATENT (OFFICE.

cums NISSEN 31mm, or 'rRo'NnHJEM, NORWAY, ASSIGNOR T NORSK ALxALrA/s,

- OF TRONDHJ'EM, NORWAY.

APPARATUS ron THE ELECTROLYSIS or sonu'rrons or ALKALINE GHLORIDS.

Application filed December 12, 1918. Serial No. 266,519.

- v To all whom it may camera:

Be it known that I, CLAUs NISSEN RIIBER, of Hans Hagerups gate 8, Trondhj em, in the Kingdom of Norway, have invented certain new and useful Improvements in Apparatusfor the Electrolysis of Solutions of Alkaline Chlorids; and I do hereby declare the following to be a full, clear, .and exact description of the invention, such as 'will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon, which form a part of this specification.

This invention relates to the electrolysis of solutions of alkaline chlorids in ap aratus with horizontal or substantially contaminated with carbon dioxid and oxy gen, which render the further utilization of the gas diflicult, the anodes are attacked by nascent oxygen, which results from secondaryreactions and the diaphragm is successively dissolved by the strong hydroxid solution.

The object of the present invention is to eliminate these drawbacks. The construc tion of an apparatus, which could be used for carrying this invention into effect is diagrammatically illustrated in the accompanying drawing in whichigure 1 represents a vertical section; and

Fig. 2 a vertical section taken at right angle to the section shown in Fig. 1.

A shallow case (1) of metal for instance copper or iron, which in the illustrated example serves as cathode chamber and container for the resulting hydroxid solution is at the top provided with a grate of metal rods (2) of a rectangular section arranged near to one another. The dia hragm (3) is supported upon this grate. %n this case is placed a frame (4) made of concrete, shale slates .or other material, which resists the action of the substances present. This frame which constitutes the anode compartment is at the top provided with a cover (5) of the trode carbon Specification of Letters Patent. I Pate fed M 17 1921 same kind of material as the frame itself and carries at the lower part the horizontal anodes (6), which as usual consist of elecartificial graphite or magnetite. 5

A characteristic feature of the apparatus consists in the construction of the diaphragm and the manner in which it is produced.

It is old to constructhorizontal dia phragms by placing upon a metal wire nett ng an asbestos plate through which the liquid has to pass. This arrangement, however, has the drawback that the asbestos plate does not at every point lie in exact contact with the netting. Further such plates will easily obtain cracks, through which the prilici al quantity of the salt solution may pass. oreover such long fibrous asbestos which must be used in the manufacture of abestos boards or paper shows a comparatively low resistance to hyprochlorites, and alkaline hydroxid so that the manufacture of strong hydroxid solut1ons is rendered impracticable. It has also been, attempted to use absestos cloth,-

wh'ich could be covered with a layer of a pulverulent body such as sulfate of barium. This arrangement" exhibits the fundamental disadvantage that the salt solution has not the same velocity at all parts of the diaphragm. It is obvious, that in the interstices between the individual threads of the asbestos clothl the velocity will be greater than right through a thread because in the latter instance the assage meets a much greaterresistance. uch a difference in velocity however involves a decrease in current output. The movement of the salt solution toward the cathode as will be understood has for its object to force thewandering hydroxyl-ions back and this result can be attained only for that portion, which passes between the threads, while the movement of the liquid right through thethreads is too slow to counteract the movement of the ions to any considerable extent. Also in this instance that sort of asbestos, which must be. used inasbestos cloth has a lower resistance against the action of strong by droxi'd solutions. Furthermore the present types of horizontal apparatus show the disadvantage that the meshes of the-cathode netting are too" large. It is obvious, that. when these meshes are comparatively large,

salt solution which nearly, completely escapes the top side of the metal netting must find its .way downward through the meshes,

these latter cannot be so small that the capillary force resists. the passage of the. hydrogen to such a degree that the hydrogen insteadpf passing downward forces its way right throughthe diaphragm body up into the anode compartment.

The apparatus constructed according to the present invention is provided with as finemeshes, (at least 25 andtusually 400-1000 meshes on the square centimeter) as it is pos sible to use when the capillary force is considered. Hereby it is made possible that the places on the underside of the diaphragm, through which the current doesnot pass, are practically eliminated, The advantage is hereby obtained that the hydrogen when escaping blows the formed hy-' droxid solution down into the bottom of the cathode compartment, s that it is removed from .the lines of current at the same time as it is prevented from entering by diffusion through the diaphragm.

Since the meshes are small the formed alkaline hydroxid solution will for a moment fill up the interstices of the meshes and at the next' moment the hydrogen produced,

which must force its way downward will breach through this film of liquid and blow the hydroxid solution as small drops down into the container. A regular shower of hydroxid solution is hereby produced and removed from the cathode.

The principal advantage of the fine metal netting, however, consists therein that it allows the production of a diaphragm without agglutmants from asbestos wool, asbestos flour, glass wool or other fibrous or pulverulent material with ca acity of resistance directly upon the meta netting.

For this urpose a paste or semiliquid suspension 0 lthe asbestos -wool or powdered asbestos is uniformly spread upon-the wire netting and the wateris removed by free dropping or by means of suction, that is substantial-ly in the same manner as is usual in the manufactur of paper or paste-board.

Such a coating will show the advantage of beingeverywhere in intimate contact with the surface of the wire which is of greatest importance for the electrolysis. It is obvious that if parts of the cathode are not in direct contact with the diaphragm, th'e passage of the electrical currentwill be prevented and the wire as a consequence of theevaporation taking place will be liable to coating of cement mortar. During the electrolysis gaseous hydrogen is constantly evolved on the top side of the wire net-tingv or screen at the pointwhere the particles of the diaphragm rest and it might be feared that this gas would gradually loosen the particles, so that they could be washed down into the cathode compartment by the hy droxid solution while the gas would constantly work its way up through the loose mass and finally enter into the anode compartment. Experiments havegiven the surprising result, however, that this fear is quite groundless.

The powdered asbestos necessary for this purpose need not contain long flexible fibers but can consist of short igid needles, which as experience has she n have a greater power of resistance a ainst the act-ion of h ochlorite and caustlc solution.

diaphragm of this nature is also in other respects of special advantage. In a good diaphragm. all pores and interstices should as fa as possible be of equal size. If this is not the case the movement of the salt solution will substantially be limited to the large pores, while the hydroxyl-ions wander as quickly through small as through large pores. l

Pores which are as like in size as possible can in the present instance be obtamed by the use of washed asbestos flour, that is a powdered asbestos having particles of a size as equal as possible.v The coarser powder is then placed at the bottom. Upon this is placed the powder of middle size and at the top the finest washing fraction. ,This latter above-the layers of asbestos a coating of a fine powder which is able to resist the chemical actions, 1n quest1on such as calcined alumina, silica, iron oxid, sulfate of barium and the like.

On the top of the diaphragm itself may be suitably be placed a-layer of a loose substance for instance glass wool or asbestos masses Wool of a long fibrous'character'to prevent taminating the diaphragm mass proper. It

will be understoodthat the material in the type of diaphragm above described has the advantage as compared with plates, cloth and the like that it can be used anew after a simple refining by washing, when after an extended useit has, been removed. Such previously employed mass is even better than freshly prepared mass because such small quantities of soluble substances as may be present are removed by the passage of the electrolyte.

It is an important condition for obtaining a good current output that the current density is the same at every point of the cathode netting. As this latter according to the present invention 'must have small meshes andconsequentlyalso fine threads it will have a low power of conduction. It is therefore necessary to take specialv measures to assure a uniform current density. The netting itself should be made of a metal of very good conductivity for instance of copper but preferably of silver. More especially however, the desired abundant supply of current may be obtained by supporting the netting upon a row of metal strips (2, 2 arranged near to one another. These strips should be made of copper or. other suitable material.

v This strong supporting structure of strips also has the effect that the diaphragm lies quite horizontal and does not yield under the weight of the anode liquid, this'being of importance for the eflicient working of the diaphragm.

The described fine netting may be suspended directly on the said strips or an interposed perforatedinetal sheet or upon another wire netting, which then should have meshes of a larger size. By means of these arrangements a still more uniform density of current is attained.

'The'advantageousworking of the horizontal arrangement of electrodes being due to the formation of layers care must be taken that no currents are produced in the anode liquid, whereby th e different horizontal laye-rs of the liquid are mixed with one another.

It is of particular disadvantage in this respect that the diaphragm on account of its electrical resistances produces heat which may cause the liquidat the bottom of the anode chamber to rise, while the loss ofheat through the side Walls and the cover of the anode com artment effects a cooling of the higher pos tioned part of the liquid, so that I it will descend. These. circumstances both promote an injurious flow of currents.

I The currents maybe counteracted by heating the salt solution before it is introduced into the electrolyzing chamber through the pipes (8, 8, 8).

According to the present invention the formation of currents can be further counteracted by heating the walls of the anode walls of the electrolyzing chamber can be" effected by means of electric current, the

conductors (10, 10) passing current to the horizontal anodes being given such a small sectional area that the desired heat of resistance is produced. Also other parts of the anode chambermaybe heated by electri cal resistance heat where this is found to be desirable. The horizontally positioned anode rods (6, 6, 6) are in the illustrated example at the ends provided with inclined surfaces corresponding td inclined surfaces on the conductors (10, 10). The rods can then easily be put into their proper place by beingpressed downward, whereby they are wedged so tight that a good contact is attained.- This arrangement also allows of easily removing the anode rods, when-they must be shifted or the diaphragm is to be ins ected. f claim Y 1. The method of making diaphragms for use in electrolyte chambers which consists in securing upon a metal netting a fibrous material in. a substantially pulverulent condition without an agglutinent, from a liquid containing the material in suspension.

2. For use in an electrolytic chamber, a' diaphragm including a metal netting and fibrous substantially pulverulent material deposited thereupon without an agglutinent from a bath containing the material 'in suspension. v

3. Device according to claim which the material is asbestos. s

4. Device according to claim 2 in which" the netting has at least 25 meshes per square centimeter. a

5. Device'according' to claim 2 in which the material'is arranged in layersof different degrees of fineness from the netting upwardly. Q

.6. Device according to claim 4: includin underthe netting one or more. reticulate metal structures of larger mesh than the netting. v

7. An electrolytic chamber including a horizontal diaphragm 'oom osed of a wire netting and fibrous substantially pulverulent.

material deposited thereon without an agglutinant from a bath containing the material in suspension and dividing the chamher into a cathode compartment and an anode compartment.

8; An electrolytic chamber of the character. described,'including a diaphragm sepa 10- ment against heat exchange with the outside.

rating the chamber into a cathode compartment and an anode compartment, electrodes and means for insulating the anode compart- 9. An electrolytic chamber of the character described, including a diaphragm separating the chamber into a cathode compartment and an anode compartment, electrodes and electric conductor means leading from the anodes, said conductor means including a, resistance element W1th1n the chamber for liberating heat. v

10. Apparatus accordlng to claim 9 in which the said resistance element extends 1 along a wall of the chamber and is connected to all the anodes.

11. Apparatus according to, claim 9*in which the said resistanceelement is substanv avalso slanting downwardly converging end surfaces and conductor elements supported upon opposite walls of the chamber having inclined faces adapted to form seats for the, ends of the rods.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses. i

OLAUS NISSENIRIIBER.

Witnesses:

' J. H. STAL,

T. REICHEL. 

